Mechanical percussion fuze for rockets



A ril 2, 1968 MARCHIARO MECHANICAL PERCUSSION FUZE FOR ROCKETS 2 Sheets-Sheet 1 Filed Oct. 10, 1966 QECWY A E (5 6 fizz/1W WW2 M Law 14 2 April 2, 1968 E- MARCHIARO MECHANICAL PERCUSSION FUZE FOR ROCKETS 2 Sheets-Sheet F Filed on. 10, 1966 L EB U 2 1 BHMMIBQJEJ M Jig. 5

United States Patent Ofiice 3, 5,7 MECHANICAL PERCUSSION FUZE FOR ROCKETS Ettore Marchiaro, Colleferro, Rome, Italy, assignor to BombriniaPar-odi-Delfino S.p.A., Rome, Italy Filed Oct. 10, 1966, Ser. No. 585,651 Claims r y, app ic tion It y, Oct- 2 6 2 Claims. or, 102978) A e h nica p u si n fuze for. ro ke h g an impact sensitive assembly including a spring loaded ri er. The expl e rain in l e ro or. a primer contained in the rotor and a detonator, A first safety inertia device has a eylindrical housing with a first, cylindria p p n A r ng abuts on aid fir t sp ing d, i slidably arranged on the inner wall of the housing. A plurality of first spheres are arranged circumferentially within the ring. A second safety inertia device includes a second spiral spring with a cup abutting on the second spring arranged coaxially to the striker. A plurality of second spheres are arranged circumferentially within the cup. A third safety inertia device including a striker guide tube is axially displaceable within the cup towards the rocket tip through an opening provided in the cylindrical housing and a third spiral spring is provided acting on the striker guide tube. The guide tube is retained in the inoperative position by the plurality of second spheres arranged between an inclined surface of an annular projection of said guide tube and the inner upper surface of the housing.

The present invention relates to a mechanical percussion fuze for spinning or non-spinning rockets. As it is well known, in case of rockets, unlike artillery projectiles, the accelerated motion phase (50-100 g) persists outside the launching tube, i.e. approximately until the propellant is burned out.

More particularly, the invention relates to a mechanical percussion fuze for rockets which, although being of ex treme simplicity in construction, satisfies all safety requirements. In particular, the new fuze is provided with handling safety, intended to prevent the operation of the explosive train as a result of an accidental drop during handling and transport and of the so-called flight-safety, in order to ensure the same security if an accidental impact were to occur on an obstacle situated close to the launching post.

The working of said safeties is based on the exploitation of the inertial forces arising during the accelerated motion phase of the rocket. To this end, the mechanical percussion fuze according to the present invention comprises prevention devices which do not allow the actuation or alignment of the explosive train, formed by a primer and a detonator or booster, when the fuze is subject to an impact or to vibrations only, but which ensure the said alignment after a definite interval of time elapsed from the instant at which the ballistic forces accompanying the movement of the rocket carrying the fuze begin to act on the latter.

The fuze according to the present invention has the following features:

(a) Its arming action is assured by displacement of inertial masses only.

(b) The said arming moreover depends solely on the action of the forces arising during axial acceleration, so

that the said fuze may be employed for all kinds of rockets that is to say irrespective of whether these rotate about their axis in flight, or not,

(c) Its flight safety remains in being throughout the period of accelerated motion of the rocket carrying the said fuze;

(d) A system ensuring its handling safety, which will be described in particular in the following.

The invention will now be described with reference to the accompanying figures, which show a preferred form of embodiment of the invention, but in no restrictive sense.

FIGURE 1 shows an axial section taken through the new fuze in its condition prior to firing for launching.

FIGURE 2 shows a cross-section of the fuze taken along the line 22 of FIGURE 1.

FIGURE 3 is an axial section of the same fuze in the state preceding its arming, and

FIGURE 4 is a similar view in the armed position.

With reference to these figures, the new fuze according to the invention comprises substantially:

(a) An assembly sensitive to impact formed by a cap 1, spheres or balls 2 having the function of transmitting the impact energy when the fuze hits the target, the striker or firing pin 3, and the spring 4,

(b) The explosive train formed by the primer 5 contained in the rotor 15, and by the detonator or booster 6,

(c) The mechanical system organised to ensure handling safety and flight safety, which comprises the ring 7, the springs 8, 9 and 14, the rings of balls 10 and 13, the small cup or the like 11, the striker guide tube 12 and the case 18 containing all the elements of this mechanical system.

Normally the fuze is in the safe condition since the said explosive train is interrupted owing to the fact that the primer 5 is turned through from the line of action of the striker 3, as apparent from FIGURE 1.

Therefore, accidental operation of the impact sensitive assembly cannot affect the primer. Even if the latter were to function owing to unforeseen circumstances, its detonation cannot be transmitted to the detonator or booster 6, since, in addition to being out of alignment with. the booster, said primer is protected by the surrounding metal structures of the fuze.

The condition required to allow the new fuze to operate is that it should be exposed to an axial thrust or acceleration in the forward direction, that is to say from the tail towards the tip or nose of the rocket, that this acceleration should reach a definite magnitude (for which the said fuze may be preset by means of expedients known in the art), and that it should persist for a certain time moreover.

In its operating conditions, that is to say when the said fuze is exposed to an axial acceleration of sufiicient force and duration, the ring 7 overcomes the resistance of the spring 8 and is displaced rearwards, thus allowing the ring of balls 10 to emerge from its seat or housing.

Owing to the persisting action of this acceleration, the small cup 11 acting by inertia on the spring 9 moves rearwards, since it is no longer obstructed by the balls 10 which have been displaced from their position.

Together with these displacements, the striker guide tube 12 moves rearwards under the action of acceleration, sufliciently to release the balls 13, which latter can thus travel to the periphery, running along the sloping surface of the said tube 12 and that of the small cup 11 which, in the meantime, has been displaced to its end-of-travel position, as apparent from FIGURE 3.

The said balls are thus so positioned that they cannot prevent the subsequent forward displacement of the striker guide tube 12 which precedes the arming of the fuze.

When the propellant of the rocket has been exhausted, the said acceleration ceases or even assumes a negative value owing to the resistance of the air, and the striker guide tube 12 may then be displaced forwards by the spring 14, towards the tip or nose of the rocket.

The rotor 15 is thus released from the abutment established by the terminal portion of the striker guide tube 12 which portion penetrates in a special cylindrical housing provided in the body of the said rotor and can turn about its own' action under the axis of the pre-loaded spring 16, thus bringing the primer 5 into alignment with the striker 3 and with the detonator 6.

The fuze is thus armed, as apparent from FIGURE 4, its flight safety' having been operative throughout the period of accelerated motion of the rocket.

The two spheres 17 shown in FIGURE 2 have the function of centering the rotor and to facilitate its rotation reducing possible friction. The displacement of the rotor 15 is limited by two stops or the like. The spring 16 retaining a light loading in the said end-oftravel position ensures that the primer 5 remains in alignment even under the action of vibration and of opposing inertial forces.

An acceleration of very great magnitude but of very short duration, such as may occur if the rocket were to be dropped, would 'not cause the said fuze to be armed. This applies moreover to the action of blows, series of vibrations, jolts, shocks and the like.

In the most unfavourable case, that is to say that of a drop in the axial direction causing the ring 7 acted upon by inertial force to overcome the resistance of the spring 8, the duration of this force will always be much shorter than the time required after complete translation of the ring 7 to allow the small cup 11 to be lowered, which represents the condition required to cock or arm the said fuze, thus ensuring handling safety.

On the contrary, the ring 7 is thrust forward by the spring 8 immediately after the impact, thus restoring the initial safety condition and consequently allowing the normal working of the f-uze on hitting the target.

The new fuze device may be employed in a great many conditions observed in practice, and may be adapted to these by appropriate adjustment, calibration and the like of its components.

According to another form of embodiment of the fuze according to the present invention, the said assembly sensitive to impact force may be replaced by a gunpowder firing device of the percussion type, which may be arranged to set off the primer 5 by propagation of the flame through the hollow tube 12.

The present invention is evidently not limited to the preferred form of embodiment described and illustrated, nor to that referred to above, and modifications of detail and arrangement, as well as technically equivalent devices, may be incorporated therein without thereby exceeding the scope of the invention.

What -I claim is:

1. A mechanical percussion fuze for rockets comprising in combination an impact sensitive assembly including a spring loaded striker, an explosive train including a rotor, a primer contained in said rotor and a detonator; a first safety inertia device including a cylindrical housing, a first cylindrical spiral spring arranged in said housing, a ring abutting on said first spring and slidably arranged on the inner wall of said housing and a plurality of first spheres arranged circumferentially within said ring, a second safety inertia device including a second spiral spring, a cup abutting on said second spring and arranged coaxially to said striker and a plurality of second spheres arranged circumferentially within said cup, a third safety inertiadevice including a striker guide tube axially displaceable within said cup towards the rocket tip through an opening provided in said cylindrical housing and a third spiral spring acting on said striker guide tube, said guide tube being retained in the inoperative position by said plurality of second spheres arranged between an inclined surface of an annular projection of said guide tube and the inner upper surface of said housing.

2. A mechanical percussion fuze as claimed in claim 1, 'wherein said primer contained in said rotor is arranged perpendicularly to said striker in the nonarmed position of the fuze, said rotor being retained in said position of the primer by the lower end of said guide tube, a preloaded spiral spring being provided for rotating said rotor to bring said primer in axial alignment with said striker when said rotor is disengaged from said guide tube.

References Cited UNITED STATES PATENTS 1,352,543 9/ 1920 Schneider 10280 2,625,881 1/1953 Rabinow 1()278 2,923,242 2/1960 Kl-air 10278 2,938,463 5/1960 Jasse 10278 X BENJAMIN A. BORCHELT, Primary Examiner.

G. H. GLANZMAN, Assistant Examiner. 

